Centrifugal pump



May 28, 1935. F. B. ALLEN CENTRIFUGAL PUMP Filed Aug. 2l, 1930 2 7 4 il M l c w Il ...H HMH 5 l l l Q f KA 5 o Xxx.

` 5:7 FFAA/KB AAE/v Patented May 28, 1935` t CENTRIFUGAL PUltIP Frank B. Allen, Lower Merion Township, Montgomery County, Pa., assgnor to The Allen- Sherman-Hoff Company,

Pennsylvania a corporation of Application August 21, 1930, Serial No. 476,734

6 Claims.

This invention relates to the art of pumps and pumping and more particularly to centrifugal pumps for pumping liquids containing abrasive materials.

The common types of pumps in use today are not well adapted to pump liquids containing abrasive materials, such as the ashes from coal-burning furnaces, because of the wear caused on the pump parts by the passage of the abrasive-carrying water through the pump. In centrifugal pumps particularly, the clearance spaces between the rotating parts and the stationary parts must be kept small to secure eilicient operation of the pump. In the ordinary form of centrifugal pump these spaces become worn and enlarged when abrasive carrying liquid is pumped, thus allowing excessive leakage and resulting in a serious decrease in pump efliciency.

Various ways have been suggested for preventing wear in centrifugal pumps which are intended for use with abrasive carrying liquids, among which maybe noted my co-pending U. S. patent application, Serial No. 368,289, led June 4, 1929. This application discloses a centrifugal pump in which the harmful abrasive materials are positively prevented from entering the small clearance spaces. In this type of pump, clear water is forced through the clearance spaces into the pump casing under higher pressure than the pressure within the main pumping chamber. However, in the apparatus disclosed in my application, Serial No. 368,289, a considerable quantity of the high pressure clear flushing `water passes into-the main pump casing through the clearance space between the inner edge of the impeller and the end of the pump intake pipe. -At this point the pressure of the abrasive carrying liquid is comparatively low and, as the pressure of the clear liquid is comparatively high, there is a relatively large pressure differential between the clear and abrasive liquids. This causes a considerable ow of clear liquid through the clearance space into the main pump chamber and, although this in itself is not harmful, it does result in a somewhat wasteful use of the clear water and decreases the amount of abrasive liquid which can be pumped.

It is among the objects of my present invention to provide a centrifugal pump in which the clearance spaces or communicating passages between the rotating and stationary parts will be continuously ushed and kept clear of abrasive material and inwhich the pressure of the clear water at the clearance space adjacent the pump intake will be only slightly greater than the pressure of the abrasive-carrying liquid within the pump intake. Y

Another object is the provision of a centrifugal pump having means for forcing clear water through the passages into the main pump chamber under pressure greater than that which exists-in the main chamber at the respective passages.

A further object is to provide a centrifugal pump in which the kinetic energy of pumped clear water inthe auxiliary chambers is converted into static energy which is effective to force the clear water steadily into the main impeller chamber against the existing pressure therein at the respective communicating passages between the main and auxiliary chambers.

The above and other objects of my invention l In the vertical centrifugal pump illustrated in the gure the impeller 50 is mounted on a vertical shaft 5I and is enclosed in the main pump casing 52. The shaft 5l may be driven by any suitable source of power such as an electric motor and extends upwardly through the top cover plate 53 of the sump. 'The pump casing 52 is provided with an inlet pipe 54 and a discharge pipe 55. 'Ihe liquid to be pumped is drawn up through the pipe 54 by the main impeller blades 56 and is thrown out into the annular chamber 51 by the centrifugal action of the rotating impeller in well known manner. The top and bottom cover plates 58 and 59 together with the impeller 50 and the main casing casting 52 divide the interior of the pump into the main pumping chamber 51 and the auxiliary chambers 60 and 6 I.

The impeller 50 in addition to the main blades 5B carries auxiliary impellerl blades 62 and 63, which are secured to the main impeller by the tie bolts 64. These tie bolts 64 extend through holes in the webs 65 of the main impeller and hold the auxiliary impeller blades securely in position. The auxiliary blades 62 rotate in the auxiliary chamber 60 and the auxiliary blades 63 rotate in the auxiliary chamber 6|; A

The auxiliary chamber 60 is divided intor two parts by the baille disc 66 -which is spaced from 4but carried by v4cover plate 58. In like lmanner chambers 68 and 69 respectively. These chambers 68 and 69 are connected to a supply of clean ushing water, by means of the pipes 10, 1| and 12. The pipe 12 may be connected to any suitable source of flushing water. The periphery of impeller 58 has a running t with the casing 52, and the auxiliary impeller blade castings have running ts with the inner edges of the discs 66 and 61.

A spring-pressed sealing ring 15 has a sliding Y t on the inner end of the intake pipe 54 and is adapted to have its end surface pressed into abutting contact wtih the inner edge of the impeller 50 by the spring 16. This sealing member 15 is cylindrical in form and is provided with slots 11 through which the screws 18 extend. These screws 18 are secured to the intake pipe 54 and prevent'rotation of the sealing member 15/ while permitting a limited longitudinal movement thereof. The inner edge of the casting carrying the auxiliary blades 63 is sealed by the member 19, which has a sliding t within the end casting 59 and is spring-pressed against the auxiliary irnpeller blade casting. A similar sealing member is provided to seal the inner edge of the casting carrying the auxiliary impeller blade 62. This sealing member 8D is prevented from rotating while having a limited longitudinal movement by means of a slotted portion engaging the screw 8|. The sealing member 19 may be similarly guided.

The drive shaft 5| has a bearing which may be generally designated as 82 and which is located. The lower immediately above the impeller 50. end of the bearing 82 lies within the chamber 68 and is provided with a iloating sealing member 83. This sealing member 93 is generally similar to that described and claimed in the co-pending United States patent application of L. E. Mylting Serial Number 491,140, filed Oct. 25, 1930, and comprises essentially a cup-shaped member having a close'sliding t on the outside of the bearing 82 and being spring-pressed into abutting contact with the end of the hub of the -impeller v5|) to prevent the inflow of water into the bearing. The shaft 5| is of reduced diameter immediately above the bearing 82 and is surrounded by a tubular sleeve 84 which extends upwardly and terminates in a cup 85. This cup 85 forms an oil reservoir from which lubricating oil flows down around the shaft 5| to the bearing 82,\where the spiral groove 86 coacts with the rotating shaft to form a pump drawing the oil down and thoroughly lubricating the bearing, then forcing it back up through the pipe 81 and discharging it over the bearing 88 at the upper end of the shaft 5|. The oil flows over the bearing 88, continuously lubricating it, and then to the reservoir cup 85. It will be seen that by the above described apparatus, a circulating lubricating oil system is provided by which both the upper and lower shaft bearings are thoroughly and positively lubricated.

. The shaft 5| and the sleeve 84 are surrounded by the tube 89 which is secured to the end plate 58 of the pump. This tube 89 extends upwardly and forms a stand pipe in which the clear flushing liquid which enters through the pipes 10 and 1| may rise. An overflow opening 90 is provided near the top of the stand pipe 89 and this overilow may be above the level of the sump overflow, so that the clear flushing liquid may be' maintained at a greater head than that of the abrasive-carrying liquid which is being pumped. This construction .eliminates any possibility of the abrasive-carrying liquid backing up into the communicating passages between the auxiliary and main pumping chambers when the pump is stopped.

A oat type of oil level gauge 9| may be connected to the oil reservoir cup 85 by a pipe 92 which passes through the overflow opening 90 in the stand pipe 89.

When this pump is operating, the abrasivecarrying liquid is drawn up through the inlet pipe 54 and discharged by the main impeller blades 56 through the annular chamber 51 and the discharge pipe 55. The auxiliary clear flushing water enters the auxiliary chambers through the pipes 1|) and 1| and is thrown out by the auxiliary blades 62 and 63 into the auxiliary whirl chambers between the walls 58 and 59 and the discs 66 and 61. The clear water thrown out by the auxiliary impeller blades 62 and 63 is then directed back inwardly between the discs 66 and 61 of the walls 93 of the main pump casing 52. As the pressure within the main pump chamber 51 is less than that in the auxiliary chambers 60 and 6|, there will be a positive flow of clear ilushing water through the passages 13 and 14. This iiow prevents the wearing of the small clearance spaces between the stationary and rotating parts of the pump by the abrasive action of the pumped liquid.

At the joint 94 between the sealing member 15 and the inner edge of the main impeller 50, the abrasive-carrying liquid to be pumped is at comparatively low pressure. This joint isalso protected by a positive flow of clear flushing liquid from the chamber 69. To provide this positive flow it is only necessary to supply clear water through the pipe 1| at slightly greater pressure than that which exists at the point 94 within the pump. The reason for supplying the clear water to the chamber 69 ata pressure only slightly greater than the pressure of the abrasive liquids within the pump intake is to create a positive flow of clear flushing water through the joint 94 and thus prevent abrasive wear of this joint. By limiting the pressure differential at this point to a relatively small quantity the amount of flushing water which is used is materially reduced.

The sealing rings 19 and 80 serve to prevent the ilushing water which is thrown out into the auxiliary chambers 60 and 6| by the auxiliary impeller blades from flowing back into the chambers 68 and 69. Thus it will be seen that the pressure of the clear ilushing water adjacent the joint 94 will be substantially that of the supply line 12, while the pressure within the chamber 6| will be increased by the auxiliary impeller blades to a point suflicient to cause a positive flow of ushing water through the joint 14 into the main pumping chamber. The ilow of clear water will be from the auxiliary chamber into the main chamber even though the auxiliary impeller blades be of the same diameter as the main impeller blades, because the outlet from the auxiliary chambers is relatively restricted and a greater pressure will bevbuilt up within the auxiliary chambers than will be built up by the main impeller blades in the main chamber, the outlet from which is relatively unrestricted.

From the above description, it will be seen that the pump illustrated in the ligure is adapted to pump abrasive carrying liquid without danger oi?v wear due to the abrasive action of the gritty material in the spaces between the relatively moving Darts. In my preferred pump construction there is created a relatively small pressure differential at each Joint where abrasive material might do damage. This pressure differential causes a positive ilow of clear ushing water through the joint, preventing the inilowof abra'- sive material. By maintaining the pressure differential small, the consumption of clear water is maintained at the most economical point, and the elciency of the pump is increased.` o

By making the auxiliary chambers 60 and 6| relatively large and dividing them into two parts l V by the baflies 66 and 61, the kinetic energy or velocity of the clear liquid, as it is thrown'out bythe auxiliary impeller blades, is converted into static energy or pressure at the joints 13 and 14. This construction gives a more even and positive flow of clear water through the joints 13 and 14 than it is possible to obtain when the discs 66 and 61 are omitted or the auxiliary chambers and 6| are made too small. Pumps Fof the type illustrated in the figure are frequentlyl installed in sumps and, as noted in the description, by locating the overflow opening in the tube 89 above the overflow level of the sump (indicated by dot and dash lines) the pressure of the clear ushing water will always be greater than that of the abrasive carrying liquid which enters the pump.

While I have described the illustrated embodiment of my invention in some detail, modications and variations thereof may appear to those skilled in the art to which it appertains. and I do not therefore, limit myself to the precise details shown and described, but claim as my invention, all embodiments thereof, coming within the scope of the appended claims.

` I claim:

1. A centrifugal pump having main and auxiliary impellers, a housing having a main chamber and auxiliary chambers on either side thereof. communicating passages between said main chamber and said auxiliary chambers, and means for converting velocity iluid pressure in said chambers into static pressure effective in said communicating passages, said means comprising a disc in each auxiliary chamber integrally formed with said housing and dividing the chamber into two portions, one portion communicating directly with the auxiliary impeller to receive main chamber, means disposed in said housing for effecting uid pressures in said main and auxiliary chambers, communicating means between said auxiliary and said main chambers. and means disposed in said auxiliary chambers for converting velocity fluid pressure in said auxiliary chambers into static pressure effective in said communicating means.

3. A centrifugal pump having a main chamber and auxiliary flushing water chambers, main and auxiliary impellers in said chambers respectively and means including a disc in each of said auxiliary chambers for converting the velocity fluid pressure created by said auxiliary impellers into static pressure.

4. A centrifugal pump having main and auxiliary impellers, a housing having a main chamber and auxiliary chambers on either side thereof, communicating passages between said main chamber and said auxiliary chambers, and means disposed in said auxiliary chambers for converting velocity uid pressure created therein by the auxiliary impellers into static pressure effective in said communicating passages, said means comprising a disc integrally formed with said housing, in each auxiliary chamber, the inner edge of said disc being disposed in said chamber in alignment with one wall of said auxiliary impeller.

5. A centrifugal pump having main and auxiliary impellers, a housing having a main chamber and auxiliary chambers on either side thereof, communicating passages between said main chamber and said auxiliary chambers and means for converting velocity uid pressure in said chambers into static pressure effective in ,said communicating passages, said means comprising a disc in each auxiliary chamber integrally formed with said housing and dividing the chamber into two portions and apertures at the periphery of said disc to eiect communication between said portions.

6. In a centrifugal pump, a housing having main and auxiliary chambers, said auxiliary chambers being disposed on opposing sides of said main chamber, means disposed in said housing for effecting uid pressures in said mainand auxiliary chambers, communicating means between said auxiliary and said main chambers,

and means disposed in said auxiliary chambers for converting velocity iluid pressure in said auxiliary chambers into static pressure effective in said communicating means, said means com- 

